An 83-year-old woman was hospitalized with numerous bite wounds after being attacked by a rabid beaver while swimming in Lake Barcroft near Bailey's Crossroads.

An onlooker repeatedly struck the 35-pound animal with a tree branch and then threw a fish net over it. Fairfax County Animal Control officers arrived on the scene and euthanized the animal.

The beaver tested positive for the rabies virus, officials said.

Lake Barcroft resident Mike Korin was fishing at the time Lillian Peterson was attacked.

"I saw the beaver acting abnormally; there were lots of splashes," Korin said. "About 10 minutes later, I heard a swimmer screaming for help. I boated over to her, administered first aid and called 911."

The attack, which occurred about 6 p.m. Tuesday, is the second in Virginia since mid-July, when two sisters swimming in Lake Anna in Spotsylvania County were bitten by a 65-pound beaver. That animal was reportedly shot with a BB gun before being transferred to a lab in Richmond, where it was found to be rabid.

A similar attacked also occurred last month in New York, where a Boy Scout leader was bitten in the chest by a rabid beaver while hanging onto a noodle float in the Delaware River. Once the man reached shore -- beaver in tow -- the Scouts used rocks to kill it.

Despite the spate of attacks, the head of a nonprofit organization dedicated to helping people learn about beavers said beaver attacks are extremely rare.

Sharon Brown, biologist and director of Beavers: Wetlands & Wildlife, has raised and aided beavers for more than 20 years. She said Wednesday that beavers are peaceful vegetarians who coexist with hordes of other animals living in their habitat and almost never attack humans.

"Beaver attacks are not on the rise," she said. "It's just not something beavers usually do. Occasionally, if a beaver feels cornered and is fearing for its life, it may attack -- but even that is rare."

Lee Walker, outreach director for the Virginia Department of Game and Inland Fisheries, said beavers are common throughout the state. Although the organization keeps no official record of beaver attacks, he said they are "pretty rare."

Fairfax County police spokeswoman Lucy Caldwell said the Lake Barcroft attack was the first in Fairfax County since at least 2000.

Caldwell said the victim was being treated with rabies-preventative medicine, and Korin said Peterson was in "high spirits" when he saw her Wednesday.

Sally Determan, president of the Lake Barcroft Association, said she has recommended that people not swim in the private lake for the time being.

"We want to consult with experts and see what, if anything, we should do," she said.

Each year, about 450 animals are submitted from within Fairfax County to be tested for rabies, and about 40 to 60 of these animals test positive, according to officials with the Fairfax County Health Department.